YAML vs YML: What's the Difference and Which One Should You Use?

 

Introduction

YAML vs YML are terms that often confuse developers, especially those new to working with configuration files. While they both refer to the same file format, the difference lies solely in the file extension. This blog post will clarify the distinction between YAML and YML, their similarities, and when to use each one.

What Is YAML?

YAML stands for "YAML Ain't Markup Language." It is a human-readable data serialization format designed to be simple and easy to understand. YAML is widely used in configuration files for software like Docker, Kubernetes, and CI/CD pipelines due to its clean syntax and readability.

What Is YML?

YML is simply a shorter version of the YAML file extension. While functionally identical to .yaml, the .yml extension exists as an alternative and is often used interchangeably. The choice of .yml or .yaml usually comes down to personal or project-specific preferences.

Key Similarities Between YAML and YML

• Functionality: Both .yaml and .yml files share the same syntax and capabilities, meaning they are entirely interchangeable in practice.
• File Usage: Any software system that supports YAML will recognize both extensions.
• Human-Readable Format: YAML (and YML) is designed for simplicity, making it easier for humans to write and understand compared to formats like JSON or XML.

Key Differences Between YAML and YML

• File Extension: The primary difference is the file extension itself. YAML uses .yaml as its standard extension, while YML uses the shorter .yml.
• Community Preference: The YAML community generally prefers .yaml because it aligns with the official YAML standard and avoids confusion.
• Legacy Systems: Some older tools and systems only recognize .yml files due to historical file extension length restrictions.

Why Two Extensions Exist

The existence of .yml as an extension dates back to limitations in early file systems that only allowed three-character extensions (e.g., .txt or .xml). As modern file systems now support longer extensions, .yaml has become the preferred choice in most projects, aligning with YAML's official documentation.

When to Use .yaml vs .yml

Choosing between .yaml and .yml depends on your specific use case:

• Standardization: If you want to adhere to YAML’s official standards, use .yaml.
• Legacy Systems: If you are working with older tools or systems that only support .yml, stick with .yml for compatibility.
• Team or Project Guidelines: Check your team’s conventions and maintain consistency by using one extension across the board.

Best Practices for Naming YAML Files

• Check Requirements: Always verify whether the tools or systems you are using require a specific extension.
• Stay Consistent: Whichever extension you choose, ensure consistency throughout your project.
• Document Your Choice: Clearly document the reasoning behind your choice of extension to avoid confusion among team members.

Common Use Cases for YAML Files

YAML files are incredibly versatile and are widely used in various software domains:

• Configuration Files: YAML is commonly used to define configuration settings for applications, such as Docker Compose (docker-compose.yaml) or Kubernetes manifests (deployment.yaml).
• Data Serialization: YAML is used to serialize structured data, making it easy to exchange between systems.
• CI/CD Pipelines: Platforms like GitHub Actions and GitLab CI/CD rely heavily on YAML files to define workflow configurations.

Conclusion

YAML and YML are essentially the same, with the only difference being their file extensions. While .yaml is the preferred standard in modern development, understanding the context and history of .yml ensures you can maintain compatibility with older systems when needed. By following best practices and choosing the extension that aligns with your project requirements, you can simplify workflows and avoid unnecessary confusion.